class Solution {
public:
    int climbStairs(int n)
    {
        vector<int> dp(n, 1);
        if (n > 1)
            dp[1] = 2;
        for (int i = 2; i < n; i++)
        {
            dp[i] = dp[i - 1] + dp[i - 2];
        }
        return dp[n - 1];
    }
};